采用混合工质的热声驱动脉管制冷实验研究

在计算了惰性气体二元混合工质的热力学参数之后,采用氦-氩混合气体作为工质来提高热声驱动脉管制冷的性能。实验结果表明,热声驱动脉管制冷机采用适当配比的氦-氩工质可获得比纯氦更加优越的制冷性能。     

氟利昂引射式制冷机的性能研究

本文研究了引射式制冷机的性能,当工质采用氟利昂时,可以利用低位热能来制冷,编制了计算机仿真程序,分析了状态参数对制冷机性能的影响。计算结果表明这一装置适合于空调系统。     

利用低位余热的喷射式制冷机性能研究

研究了使用氟利昂作为工质的喷射式制冷机的性能,编制了计算机仿真程序,分析了状态参数对制冷循环性能的影响。计算结果表明这一装置可以用低位余热驱动,适合于空调系统。     

磁制冷机和磁热泵结构设计探讨

一、前言磁制冷机具有氟里昂制冷机所没有的优异特性:无噪音、高效节能、高可靠性、长寿命;由于采用固体磁制冷工质,单位体积工质制冷能力强,使得磁制冷机结构更紧凑;特别是固体磁制冷工质完全避免了氟里昂(CFC)类制冷工质对大气层的污染,更使得人们日益重视磁制冷技术。同样利用固体磁工质磁热特性的磁热泵,由于磁热特性可逆性好,因此磁热泵也可望具有较高性能系数(COP),为众多低品位能源提供可靠高效利用方式。本文仅对其系统循环形式和设计方案作一简要探讨。     

有限热源吸收式制冷机的热力学建模与分析

考虑了有限热容、有限速率传热以及工质内部耗散的影响,建立了吸收式制冷机的热力学模型.在该模型中,吸收式制冷机被等价为一个不可逆卡诺热机驱动不可逆卡诺制冷机的联合循环系统.为描述循环的内不可逆性,引入了两个内不可逆性参数Ihe和Ir.其中,Ihe用于描述热机循环的内不可逆性,Ir用于描述制冷循环的内不可逆性.通过对给定供热率下热机热效率和给定制冷率下两热源制冷机性能系数解析表达式的推导,并根据等价系统的定义,获得了吸收式制冷机给定制冷率下性能系数的解析表达式,利用该表达式详细地分析了各参数对性能系数的影响.所得公式和分析结论对实际系统的理解、设计以及分析具有一定的理论指导作用.     

非共沸混合工质压缩制冷循环的不可避免Yong损失

以非共沸混合工质替代CFC5是比较有效的替代方案。通过对给定节点温差下的蒸发器和冷凝器内的温度匹配分析，提出利用调节非共沸混合工质的配比来优化蒸发器和冷凝器内的温度匹配，并可计算出循环的实际不可避免炯损失，从而提出采用非共沸混合工质的蒸气压缩制冷循环的实际不可避免炯损失的计算方法，并提出利用最佳配比和实际不可避免的Yong损失的计算，对各种非共沸混合工质对进行筛选，以进一步减少循环可避免的炯损失，为优化蒸气压缩制冷循环，提高循环的性能奠定基础。     

可利用低品位热源的热声驱动脉管制冷机

针对原有热声驱动脉管制冷机实验装置,改进了板叠冷端夹套式水冷却器内部的丝网填料,进一步优化了小孔阀和双向进气阀的开度,获得了116．4K的最低制冷温度。通过操作脉管制冷机双向进气阀,使系统的起振温度从560℃降低为370℃,为低品位能源的利用创造了条件。     

内可逆空气制冷机性能的生态学优化

基于[火用]分析的观点，运用有限时间热力学方法对内可逆空气制冷机进行生态学优化，导出了换热器热导最优分配时的最佳制冷功率、熵产率以及生态学（E）目标函数的解析式，进一步求得最大E目标值时的工质等熵温比（压比）界限及相应的制冷系数、制冷功率和熵产率；采用数值计算分析了热源温比、换热器总热导以及高温热源温度和环境温度之比对该制冷机生态学最优性能的影响。结果表明：生态学目标函数不仅反映了[火用]输出率和熵产率之间的最佳折衷，而且也反映了制冷功率和制冷系数之间的最佳折衷。     

非共沸混合工质压缩制冷循环的不可避免(火用)损失

以非共沸混合工质替代 CFCS是比较有效的替代方案。通过对给定节点温差下的蒸发器和冷凝器内的温度匹配分析 ,提出利用调节非共沸混合工质的配比来优化蒸发器和冷凝器内的温度匹配 ,并可计算出循环的实际不可避免灯用损失 ,从而提出采用非共沸混合工质的蒸气压缩制冷循环的实际不可避免灯用损失的计算方法 ,并提出利用最佳配比和实际不可避免的灯用损失的计算 ,对各种非共沸混合工质对进行筛选 ,以进一步减少循环可避免的灯用损失 ,为优化蒸气压缩制冷循环 ,提高循环的性能奠定基础。     

混合制冷剂HFC152a/HFC125的电冰箱实验研究

对环保节能制冷剂——二元近共沸混合工质HFCl52a／HFC125在电冰箱上应用的制冷循环性能进行了详细的理论计算和分析，并且对该工质灌注式替代CFC12和HFC152a／HCFC22在不同配比和充灌量下的电冰箱主要制冷性能进行了实验研究。实验结果表明：在合适的配比和充灌量下电冰箱制冷性能指标满足国家标准要求。混合制冷剂HFC152a／HFC125优良的环保性能和冰箱制冷性能使它完全适合做新一代的冰箱制冷剂。     

Numerical simulation of a two‐stage pulse tube refrigerator based on adiabatic model

Cryocoolers are devices that are capable of achieving and maintaining cryogenic temperatures for a number of applications such as high‐energy physics, cooling of superconducting magnets, sensors, high‐vacuum production, cryotronics, cryonics, and so on. All the above applications need coolers with high reliability, efficiency, low maintenance, and low cost. The absence of moving parts at the cryogenic temperatures makes the pulse tube (PT) coolers quite suitable for the above applications. In spite of considerable developments in the area of PT cryocoolers, many of the fundamental processes responsible for the cold production are not fully understood. In this work, we present the results of numerical simulations of two‐stage pulse tube refrigerators (PTR) using adiabatic flow of gas through the pulse tube system. A two‐stage PTR is the improved version of single‐stage system to achieve temperature close to 4 K. Assuming adiabatic gas flow through PTs, the algebraic equations for pressure, mass flow, and volumes at different locations have been derived and solved by a MATLAB based program. Using the above, the performance of PTR has been optimized for different operational parameters. The cooling powers predicted by the model have been compared with the experimental data, and they are in good agreement with each other.     

First and second law analysis of pulse tube refrigerator

The first and second law of thermodynamics was used to analyze the orifice type and the double-inlet type of pulse tube refrigerator (PTR). Detailed dynamic characteristics of the thermodynamics, flow and heat transfer processes in the PTR were revealed, including the dynamic pressure variations, transient gas temperature, mass flow rate in the PTR. The exergy loss method was used to analyze each component in the PTR for the first time, and the performance coefficients of all components of PTR have been obtained. It was found that the performance coefficient of the double-inlet PTR was 0.108, 9% higher than that of the orifice PTR. The analysis also showed that the exergy efficiency of the double-inlet PTR was 29.95%, significantly higher than that of the orifice PTR (25.04%). In addition, it was found that the exergy losses in the regenerator and orifice were substantially larger than in other components of the PTR system. The optimal design of these two key components is, therefore, essential for the further improvement of the PTR performance.     

Hydrogen tube vehicle for supersonic transport: 3. Atmospheric merit

To compare 24 common gases as potential operating atmospheres for tube vehicles, equations are derived for aerodynamic (tunneling) performance of the atmosphere and molar energy density of the tube vehicle. Aerodynamic performance is a function of the speed of sound and Reynolds number, and energy density is a function of the free energy of reduction or oxidation of the tube gas and the stoichiometric coefficients of the stored reactants. The product of these two parameters determines the rank of atmospheric merit. Hydrogen exhibits the highest aerodynamic performance, yields the fourth highest energy density, and has the highest overall merit. Acetylene, ammonia, and methane, in decreasing order, follow hydrogen in merit. Although superficially a promising tube gas, helium is below average in merit because of low energy density of the vehicle.     

非对称横槽管高效换热元件传热性能研究

基于k-ε模型,针对一种非对称横槽管换热元件,对高温高压工况下管内氦气的流动与传热进行了数值模拟研究。比较了非对称横槽管与对称横槽管的综合传热性能。同时,应用"中心复合设计"(CCD)方法对非对称横槽管的三个基本结构参数(槽间距a、槽宽b、槽深e)进行了优化设计,考察了不同结构对非对称横槽管传热性能的影响,并对其内部机理进行了初步的探讨。结果表明,非对称横槽管传热性能优于传统的对称型横槽管,最优结构参数为a12-b8-e0.6。     

Simulation of gas species and temperature separation in the counter-flow Ranque–Hilsch vortex tube using the large eddy simulation technique

A computational fluid dynamic model is used to predict the species and temperature separation within a counter flow Ranque–Hilsch vortex tube. The large eddy simulation (LES) technique was employed for predicting the gas flow and temperature fields and the species mass fractions (nitrogen and helium) in the vortex tube. A vortex tube with a circumferential inlet stream of nitrogen–helium mixture and an axial (cold) outlet stream and a circumferential (hot) outlet stream was considered. The temporal evolutions of the axial, radial and azimuthal components of the velocity along with the temperature, pressure and mass density and species concentration fields within the vortex tube are simulated. Even though a large temperature separation was observed, only a very minimal gas separation occurred due to diffusion effects. Correlations between the fluctuating components of velocity, temperature and species mass fraction were calculated to understand the separation mechanism. The inner core flow was found to have large values of eddy heat flux and Reynold’s stresses. Simulations were carried out for varying amounts of cold outlet mass flow rates. Performance curves (temperature separation/gas separation versus cold outlet mass fraction) were obtained for a specific vortex tube with a given inlet mass flow rate.     

Hydrogen and LNG production from coke oven gas with multi-stage helium expansion refrigeration

Here we propose a novel cryogenic system to simultaneously produce liquid hydrogen (LH₂) and liquefied natural gas (LNG) from coke oven gas. The coke oven gas, simplified as a mixture of methane and hydrogen, directly enters the cryogenic system. Due to the very low temperature of liquid hydrogen, helium is selected as the refrigerant, and the energy needed for the liquefaction is supplied by a multi-stage helium expansion refrigeration system. The high-purity liquid hydrogen and LNG products are obtained with the help of a cryogenic distillation column. The whole cryogenic process is simulated with the Aspen HYSYS software to determine the parameters of each process point and key component. We found that the process is able to produce LH₂ and LNG of very high purity. Using the power consumption of the product liquefaction as the major performance parameter for the analysis, optimum parameters of the multi-stage helium expansion liquefaction process could be found. The results show that the proposed system can achieve a methane recovery rate of 97.9% and a hydrogen recovery rate of 99.7% with acceptable energy consumption.     

Effect of helium xenon as working fluid on the compressor of power conversion unit of closed Brayton cycle HTGR power plant

Helium is one of the best coolants in closed Brayton cycle power plants as it has superior transport properties; however, the main shortcoming is its compression, which is very difficult to achieve. It leads to a higher number of compressor stages, means bigger mass and big size of the compressor, which create dynamic issues in a compressor of the power conversion unit. All the helium compressors ever constructed have a very high number of stages such as Oberhausen II type 50 MW and JAEA 300 MW, high and low pressure compressors have 25 and 35 stages respectively. In this paper thermodynamic traits of mixing helium with an inert gas xenon were presented. Helium xenon mixture up to the molecular weight of <40 g/mol not only increases heat transfer coefficient but also significantly increase the loading of the compressor. A 7% higher heat transfer coefficient can be achieved with 15 g/mol helium xenon mixture. Therefore, a 15 g/mol helium xenon mixture compressor was designed and its performance analysis conducted using Ansys CFX. It is found that the use of 15 g/mol helium xenon mixture greatly increases the blade loading, which gives a higher total outlet pressure ratio. The obtained results indicated that only 18.75% stages of helium xenon compressor can generate requisite outlet pressure. Hence, the use of helium xenon over pure helium is advantageous as it reduces size and cost of turbo compressor of HTGR power plant.     

单级轴流氦气压气机空气模拟气动性能数值分析

HTGR-10模块式高温气冷堆作为第四代反应堆型具有系统简单、安全可靠和经济性能优越等特点。而氦气循环透平发电机组的氦气压缩机性能,将成为发电是否高效的决定因素之一。本文利用Numeca数值模拟软件对一亚音速轴流氦气压气机试验机进行了气动性能及准数关系研究,分析了气流在叶栅中的流动机理,探讨了等雷诺数下相似准数对压气机叶片性能的影响。结果表明:采用空气工质模拟氦气压缩,在马赫数小于0.4工况下对压气机的通流流动影响很小,基本可以忽略;采用大于0.5的反动度,增加正预旋可以使效率维持较高的水平;在马赫数较小的情况下,绝热指数k不会对相似模拟产生大的影响。     

Structural optimization and experimental investigation of supersonic ejectors for boosting low pressure natural gas

The supersonic ejector was introduced into boosting the production of low pressure natural gas wells. The energy of high pressure gas wells, which was usually wasted through choke valves, was used as its power supply to boost the low gas production. The operating performance of natural gas ejectors was determined not only by the operating parameters but also by the structural parameters. This study focused on the structural optimization and operating performance of natural gas ejectors. The optimal structural parameters were obtained by numerical simulation when the maximum pressure ratio was obtained, and the numerical results were validated by experimental investigation. The numerical results showed that the optimal diameter ratio of mixing tube to primary nozzle throat was 1.6, the optimal length to diameter ratio of mixing tube was 4.0 and the optimal inclination angle of mixing chamber was 28°. The entrainment ratios and pressure ratios from the numerical simulation agreed well with the field experimental data, with the maximum value of pressure ratio up to 60%. The operating performance of the supersonic ejector was also investigated by the field experiment, and the results showed that the induced gas flowrate and entrainment ratio showed nonlinear characteristics with peak values when the motive pressure ranged from 8 MPa to 13 MPa. These experimental results have proved the optimized structural parameters of the supersonic ejector. The investigation will help to the further application in boosting natural gas production of supersonic ejector.     

天然气发动机混合器结构对混合过程影响的研究

利用纹影摄像系统拍摄得到空气-天然气混合过程的清晰图像，研究了改进的文丘里管式混合器内引流管对混合气形成过程的影响。在文丘里管式混合器内设置引流管可以改善混合器内天然气与空气的混合质量。引流管沿混合器直径方向设置，且燃气喷射与空气流动形成交叉射流可明显地改善混合过程。按交叉射流设计的翼型引流管在降低空气流动阻力的同时也可取得良好的混合效果。